• Title/Summary/Keyword: molecular ordering

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Low Spin-Casting Solution Temperatures Enhance the Molecular Ordering in Polythiophene Films

  • Lee, Wi Hyoung;Lee, Hwa Sung;Park, Yeong Don
    • Bulletin of the Korean Chemical Society
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    • v.35 no.5
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    • pp.1491-1494
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    • 2014
  • High-crystallinity poly(3-hexylthiophene) (P3HT) thin films were prepared by aging the precursor solutions, prepared using a good solvent, chloroform, at low temperatures prior to spin-casting. Lower solution temperatures significantly improved the molecular ordering in the spin-cast P3HT films and, therefore, the electrical properties of field-effect transistors prepared using these films. Solution cooling enhanced the electrical properties by shifting the P3HT configuration equilibrium away from random coils and toward more ordered aggregates. At room temperature, the P3HT molecules were completely solvated in chloroform and adopted a random coil conformation. Upon cooling, however, the chloroform poorly solvated the P3HT molecules, favoring the formation of ordered P3HT aggregates, which then yielded more highly crystalline molecular ordering in the P3HT thin films produced from the solution.

Relation between molecular structure and order parameter of liquid crystals and dyes in GH-LCD (GH형 LCD에 있어서 액정 및 2색성 색소의 분자형상과 배향질서도와의 관계)

  • 박우상
    • Electrical & Electronic Materials
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    • v.10 no.10
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    • pp.989-994
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    • 1997
  • In a Guest-Host cell the orientational ordering of dyes doped into liquid crystals has been investigated. To evaluate the influence of the host liquid crystals on the ordering of the dyes we have measured precisely the ordering parameters of the liquid crystals by using the dichroic ratio of the absorbances for infrared light polarized parallel and perpendicular to the diector. Our experimental results show that the ordering of the dyes can be expressed as a function of not only the molecular structure of the dyes but also the order parameter of the liquid crystals. These functions are dependent on the kinds of the liquid crystals and the dyes. Particularly the combination such as anthraquinone dyes doped into cyanobiphenyl liquid crystals show a very high ordering parameter. This is considered due to a strong intermolecular interaction between the dipoles of both liquid crystals and dyes.

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High Molecular Weight Conjugated Polymer Thin Films with Enhanced Molecular Ordering, Obtained via a Dipping Method

  • Park, Yeong Don
    • Bulletin of the Korean Chemical Society
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    • v.34 no.11
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    • pp.3340-3344
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    • 2013
  • The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

Two-dimensional Supramolecular Ordering via Hydrogen and Halogen Bondings

  • Yoon, Jong-Keon;Kim, Ho-Won;Jeon, Jeong-Heum;Kahng, Se-Jong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.11-11
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    • 2010
  • Supramolecualr ordering has been actively studied due to it's possible applications to the fabrication processes of nano-electronic devices. Van der Waals interaction and hydrogen bonding are frequently studied mechanisms for various molecular structures based on non-uniform charge distributions. Halogen atoms in molecules can have electrostatic interactions with similar strength. Big halogen atoms have strong non-uniform charge distributions. To study molecular orderings formed by hydrogen and halogen interactions, we chose a molecular system containing oxygen, hydrogen, and bromine atoms, a bromo-quinone. A two-dimensional molecular network was studied on Au(111) using a low-temperature scanning tunneling microscope. Bromo-quinonemolecules form self-assembled square grids having windmill structures. Their molecular orderings, chiral structures, and defects are explained in terms of hydrogen and halogen interactions.

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Electrical Characteristics Enhancement of Conjugated Polymer Thin Film Transistor by Using Dipping Method (Dipping 방법을 이용한 공액 고분자박막 트랜지스터의 전기적 특성 향상)

  • Kim, Hye Su;Na, Jin Yeong;Park, Yeong Don
    • Polymer(Korea)
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    • v.38 no.2
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    • pp.188-192
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    • 2014
  • In this work, it is possible to simply improve the molecular ordering of a conjugated polymer thin film by dipping into poor solvent. The structural order, optical, and electrical properties of poly(3-hexylthiophene) (P3HT) films were profoundly influenced by dipping time and solubility of solvent. Especially the dipping time in methylene chloride was controlled to efficiently improve the molecular ordering of the P3HT. The correlation between the structural order and the electrical properties was used to optimize the dipping time in the appropriate solvent.

Effect of the Molecular Structure of Rubbed Polyimide Films for Surface Liquid Crystal Alignment of Nematic Liquid Crystal (네마틱 백정의 표면 액정 배향에관한 폴리이미드막의 분자 구조의 효과)

  • 서대식
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.05a
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    • pp.232-234
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    • 1996
  • We have investigated the effect of molecular structure of polymer of rubbed polyimide (PI) films for surface liquid crystal alignment. To obtain surface alignment effect of Polymer molecular structure, we measured the polar (out of plane-tilt) anchoring strength and surface ordering of 5CB on rubbed PI surfaces. We have found that the polar anchoring strength of 5CB is depend on the polymer molecular structure of these unidirectionally rubbed PI surfaces.

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Distinct Mechanisms of DNA Sensing Based on N-Doped Carbon Nanotubes with Enhanced Conductance and Chemical Selectivity

  • Kim, Han Seul;Lee, Seung Jin;Kim, Yong-Hoon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.415.1-415.1
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    • 2014
  • Carrying out first-principles calculations, we study N-doped capped carbon nanotube (CNT) electrodes applied to DNA sequencing. While we obtain for the face-on nucleobase junction configurations a conventional conductance ordering where the largest signal results from guanine according to its high highest occupied molecular orbital (HOMO) level, we extract for the edge-on counterparts a distinct conductance ordering where the low-HOMO thymine provides the largest signal. The edge-on mode is shown to operate based on a novel molecular sensing mechanism that reflects the chemical connectivity between N-doped CNT caps that can act both as electron donors and electron acceptors and DNA functional groups that include the hyperconjugated thymine methyl group[1].

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Development of High-Performance Organic Field-Effect Transistors via Surface-Mediated Molecular Ordering

  • Cho, Kil-Won;Kim, Do-Hwan;Park, Yeong-Don;Jang, Yun-Seok;Hwang, Min-Kyu;Lee, Hwa-Sung;Lim, Jung-Ah
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07a
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    • pp.147-148
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    • 2005
  • We report on high-performance organic field-effect transistors by promoting surface-mediated two-dimensional molecular ordering in organic semiconductor. To achieve this goal, we have controlled the intermolecular interaction at the interface between organic semiconductor and the insulator substrate.

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